In many solar energy conversion systems, it is required that a concentrated solar collector is continuously repositioned to track and follow the sun in order to obtain efficient solar energy collection. In general, the collector is driven in either direction until the solar energy received from two tracking sensors reaches equilibrium, thus indicating that the collector is directly facing the solar rays. Such prior art tracking systems with a concentrated solar collector require at least some solar energy to be incident on the tracking sensors.
However, where solar concentrators are used for instance to increase the solar efficiency, the solar capture angle of the collector is relatively narrow. Thus, if the sun is obscured by clouds for any period of time, and the rays are no longer within the collector capture angle, the high resolution tracking sensors do not receive any or at least sufficient solar energy to drive the collector towards the desired equilibrium position where the sun will be directly incident on the collector. Several prior art solutions to this problem involve providing a separate memory unit which stores the tracking data and from which the subsequent tracking requirement can be interpolated to continue to drive the collector in the same direction. Thus, in such systems, it is hoped that the sun's rays will be within the collector capture angle when the sun reappears.
This loss of sun, however, can occur under one or more daily cloudy conditions each lasting anywhere from a few minutes to the entire day when the sunlight is obscured. In these conditions the prior art system continues to use energy to drive the collector in an attempt to locate the sun--even if there is no sun for the rest of the day. Thus, in some cases, the net system energy would be negative; i.e. the system will be using more energy to try to find the sun than the energy converted during the periods of time when the sun is out.
Accordingly, it is desired to provide a solar tracking system for solar collectors which will significantly reduce the use of energy during time periods when the sun is obscured. Secondly, it is desired to provide a system without the need for relatively expensive storage devices for storing tracking data. Also, it is desired to provide such a tracking system where the collector will automatically positioned to directly face the sun, when, after a period of solar obstruction, the sun appears unobstructed--without the need to interpolate tracking data or to track continuously during the period of sun obstruction.